1. Field of the Invention
This invention relates to personal computers and more particularly to personal computers which utilize a microprocessor that can be replaced to upgrade performance.
2. Description of the Related Art
Advancements in computer technology proceed at a startling rate. Improvements in the speed and the capabilities of modern computers advance so quickly that the preceding generation of technology has hardly reached the market before it is rendered obsolete by faster, better computers. While the pace of advancement is a marvel to scientists, engineers, and enthusiasts, it can be frustrating to the consumer trying to keep pace with the industry.
Although the price of personal computers has dropped dramatically over the last 20 years, computers still represent major investments for individual and business consumers. Unfortunately, as new technology develops, a computer becomes obsolete and its market value plummets. Consequently, replacing an old system with a new one involves spending large sums for the new computer and receiving very little return on the old one.
At the heart of advancements in computer technology lie the improvements in microprocessor performance. To receive the benefits of an advanced microprocessor, a consumer previously had to buy an entire computer and throw out his old one, possibly retaining a few interchangeable components. Although many consecutive computer designs by various manufacturers were nearly identical, the microprocessor designs varied enough that the systems were incompatible. As a result, an old processor could not be simply replaced with a new one; the entire computer had to be disposed of and replaced with a modern system.
In an effort to reduce the cost of upgrading computer systems, manufacturers began to explore ways in which the processor could be replaced and still preserve the remainder of the computer system. Some manufacturers produced computers where the microprocessor could be replaced by changing the computer's microprocessor circuit card. To improve the performance of a computer system, a consumer was only required to buy a new processor card. The old card could be removed from the computer and substituted with the new card.
Although this was an improvement, this method of upgrading remained costlier than necessary. Because the entire processor card had to be replaced, all of the circuitry, components, and chips on the old processor card were wasted. The consumer had to absorb not only the cost of the new processor, but the cost of all of the components on the new card and the expenses incurred in manufacturing the compatible card.
One side effect of the use of interchangeable processor cards is that the available space for components is relatively small. If the processor cards are large, then replacement becomes very expensive and possibly not cost effective. If the cards become too small, insufficient functions can be located on the card and performance would suffer. So space is at a premium.
One line of microprocessors in favor are the Intel Corp., which form the basis for personal computers compatible with those originally produced by International Business Machines Corp. such as the IBM PC/AT. Currently the line extends from the 8088 to the 80486. Particularly favored units include the 386SX, the 386DX, the 486SX and the 486DX, in general order of increased performance. Therefore it is common to use these microprocessors on the interchangeable processor cards. Of particular interest are the 486DX, 486SX and companion 487SX. The 486SX can be considered as an 486DX without the internal numeric coprocessor. When a numeric coprocessor is necessary, an 487SX is inserted into the system. Therefore, according to recommendations from Intel, two full sockets are necessary on the processor card to allow numeric coprocessor support. This creates major space problems on already crowded interchangeable processor cards.